This invention relates to actuators. An “actuator” is defined in the Merriam-Webster's Collegiate Dictionary, Tenth Edition as a mechanical device for moving or controlling something. Actuators perform myriad functions and enable many modern conveniences.
Aircraft for example, require actuators to fly. Flaps, spoilers and ailerons in each wing, each require an actuator. Actuators in the tail control the rudder and elevators. Actuators in the fuselage open and close the doors that cover the landing gear bays. Actuators raise and lower the landing gear. Actuators on each engine control thrust reversers by which the plane is decelarated.
In addition to uses in aircraft, actuators are used in computer disk drives to control the location of the read/write head by which data is stored on and read from the disk. Actuators are used in robots, i.e., in automated factories to assemble products. Actuators operate brakes on vehicles; open and close doors; raise and lower railroad gates and perform numerous other tasks of everyday life.
Prior art actuators fall into two general categories: hydraulic and electric with the difference between the two categories being the motive force by which movement or control is accomplished. Hydraulic actuators require a pressurized, incompressible working fluid, usually oil. Electric actuators use an electric motor, the shaft rotation of which is used to generate a linear displacement using some sort of transmission.
A problem with hydraulic actuators is the plumbing required to distribute and control the pressurized working fluid. In an airplane, a pump that generates high-pressure working fluid and the plumbing required to route the working fluid add weight and increase design complexity because the hydraulic lines must be carefully routed.
Electric actuators, which are powered and controlled by electric energy, require only wires to operate and control but a problem with prior art electrical actuators is their reliability. Windings of electrical motors are susceptible to damage from heat and water. Bearings on motor shafts wear out. The transmission between the motor and the load, and which is inherently more complex than the piston and cylinder used in a hydraulic actuator, is also susceptible to failure. While electrical actuators have advantages over hydraulic actuators, an electrically-powered actuator that provides increased reliability, would be an improvement over the prior art. Fault-tolerance, i.e., the ability to sustain one or more component failures or faults yet keep working, would provide an improvement over prior art electrical actuators.